Inducing thermo-tolerance in late sown wheat (Triticum aestivum L.) through pre-conditioning with H2O2.

Wheat is sown on 40% of the total cultivated area in Pakistan. More than half of which is sown late due to delayed harvest of cotton and rice thus making it vulnerable to sub and supra optimal temperatures (Govt. of Pakistan, 2013). Quantity and quality of late sown wheat is affected due to low temperature at earlier growth stages (Feng et al., 2008) and to high temperature at later growth stages (Farooq et al., 2011). Late sowing has become a major limiting factor for wheat productivity as temperature is rising globally (Ortiz et al., 2008; Lobell et al., 2011). It is reported that every single day’s delay after 15 Nov would bring diminution of 36 kg ha in economical yield (Subhan et al., 2004), thus reducing the wheat production up to two million tons in Pakistan (Rehman et al., 2011). The elevated temperature hampers the vegetative attributes like stem growth, number of leaves, leaf area and biomass production and also upset the photosynthesis process and enzymes activation in crops (Tahir et al., 2009; Mahboob et al., 2005). Low temperature stress causes damages to plasma membrane integrity, protein assembling, photosynthesis (Mahajan and Tuteja, 2005), physiology, allometry and yield attributes (Yu et al., 2003). Although there is no substitute to timely sowing, but techniques that can ensure fair seed emergence and stand establishment under late sown conditions could mitigate the harmful effects of late sowing. Different roles of H2O2 have been documented in crosstalk of acclimation processes in stressed crops (Mittler et al., 2004). Plants under stress always tend to produce free radicals and other reactive oxygen species (Taiz and Zeiger, 2010; Arora et al., 2007).These active oxygenated radicals predominantly H2O2 cause oxidative injury, hampered the plant defense system, denature the proteins and organelles of the cells at higher concentration. The seed treated with H2O2 proved to be more responsive to different stresses as in water deficit conditions maize leaves showed a marked increment regarding scavenging molecules (Terzi et al., 2014). The dismutation of superoxides (SOD) and catalytic activities of peroxidases and catalase (POD and CAT) enable the plant to cope with devastatingly impact of high temperatures. The pretreated tobacco plants acquired improved resistant against high temperatures as SOD and CAT actives were enhanced (Wi et al., 2010). H2O2 is renowned in acquisition of stress tolerance by procuring systematic acquired resistance and hypersensitive response (Torres et al., 2006). Till now, a little work has been reported regarding H2O2 under natural environmental conditions. So, we envisaged this study based on the hypothesis that H2O2-mediated response would markedly improve the bio-physiological attributes to induce thermo-tolerance in late sown wheat. Therefore, objective of experiment was to assess changes in growth and various antioxidants activities due to H2O2 and distilled water preconditioning in optimal and late sown wheat. Pak. J. Agri. Sci., Vol. 52(4), 945-951; 2015 ISSN (Print) 0552-9034, ISSN (Online) 2076-0906 http://www.pakjas.com.pk